Flame holding device movable between a flameholding position and a streamlined position



Dec. 30, 1958 KURT] 2,866,314

FLAMEHOLDING DEVICE MOVABLE BETWEEN A FLAMEHOLDING POSITION AND ASTREAMLINED POSITION Filed Jan. 2, 1953 INVEN TOR ALEXANDER KURT/ FLAMEHOLDING DEVICE MOVABLE BETWEEN A FLAMEHOLDLNG POSITION AND A STREAM-LINED POSITION Alexander Kurti, North Woodbury, Conn., assignor toUnited Aircraft Corporation, East Hartford, Conn a corporation ofDelaware Application January 2, 1953, Serial No. 329,367

10 Claims. (Cl. 6035.6)

This invention relates to a flame holding apparatus and moreparticularly to the type used in an afterburner of an aircraft engine.

An object of this invention is to provide a flameholder with aretractable portion which will move between a position making theflameholder streamlined, for use when there is no afterburning, to aposition making the downstream end of the flameholder a blunt end foruse when there is afterburning to effect a reduction of velocity therebystabilizing combustion at this point.

Another object of this invention is to provide a flameholder which willprevent blowout at the operating velocities of flow which pass throughthe afterburner. Since the speed of flame propagation is less than thestream velocity, it is necessary to provide a region of low relativevelocity of suificient size to establish a flame. When this flame isextinguished it is referred to as a blowout.

A further object of the invention is to provide a flameholder which willhave a minimum of pressure loss thereover during non-afterburning.

Further objects and advantages will be apparent from the followingspecification and drawings.

Fig. 1 is a view of a jet engine and afterburner combination with thegreater portion of the engine in outline form and with the remainder ofthe engine and the afterburner in cross section.

Fig. 2 is an enlarged view of the lower part of the flameholder as shownin Fig. 1 with its actuating mechanism. Fig. 3 is a view taken along theline 3-3 of Fig. 2. Fig. 4 is a view taken alongthe line 44 of Fig. 2.

With reference to Fig. l, the turbojet engine 2 shown is a centrifugaltype having its compressor 7 driven by a turbine 4. Combustion chambers5 therein deliver air from the compressor to the turbine. An afterburner6 is attached to the turbine outlet to provide a means of increasing thethrust.

Air is directed into the engine to the compressor. Compressed airdischarging from the compressor passes to the turbine 4 throughcombustion chambers where it is mixed with fuel. Fuel is delivered tosaid engine through conduit 8. The fuel-air mixture is initially ignitedwithin the combustion chambers by spark igniter 10. It is to beunderstood that any fuel supply means and ignition means for an enginemay be used.

From the turbine 4, the gases pass around a cone 12 into the diffusersection 14 of the afterburner. When the afterburner is operating, fuelis discharged into these gases from a plurality of fuel nozzles 16,connected to fuel conduit 17, located in diffuser 14. Since the gasesleaving the turbine 4 contain considerable unburned oxygen, theadditional fuel introduced by fuel nozzles 16 provides a combustiblemixture which may be initially ignited Within the combustion chamber 18by a spark igniter 28. Here again, for the afterburner, it is to beunderstood that any type of fuel supply means and ignition means for anafterburner can be used. The burning of this combustible mixture isstabilized in the combustion chamber 18 of the afterburner by aflameholder 22. A flameholder accomnite States Patent 2,856,314 PatentedDec. 30, 1958 plishes this by providing an area in which the velocitiesare maintained at a value below that at which blowout occurs. The burnedbases discharge from the engine through the nozzle 24 whose area can bevaried.

The variable nozzle 24 operates between a minimum opening for engineoperation without afterburning and a maximum opening for operation ofthe engine with afterburning. The nozzle actuating system as shownconsists of a cylinder 26, a piston 28, a nozzle control rod 30 and apiston rod 32. The variable nozzle 24 is opened or closed by admittingan actuating pressure to one side of piston 28 or the other throughconduits 34 or 36. It can be seen that if a pressure is admitted throughconduit 34 and valve 40 to the right side of pistons 28, and the leftside of pistons 28 are vented, the nozzle 24 will be moved in a nozzleopening manner, and if an operating pressure is admitted through conduit36 and valve 38 to the left side of pistons 28, and the right side ofpistons 28 are vented, the nozzle 24 will be moved in a closingdirection. While the selection and admission of this actuating pressureand venting can be performed manually, a nozzle control which willperform such function automatically is shown and claimed in U. S.application Serial No. 196,424 filed November 18, 1950, now Patent No.2,715,311.

With reference to Fig. 2, the flameholder 22 is formed of two parts 42and 44. The part 42 consists of an annular ring substantially fixedlysupported in the combustion chamber of the afterburner by a streamlinedstrut structure 46. This structure consists of a center section 48 andouter sections 50. These outer sections are mounted to allow for radialexpansion in a manner to be hereinafter described. The part 42 ishollow, being U-shaped in cross section, with its downstream end openand is formed having a cross section of the forward part of a throughare below a value suflicient to cause blowout.

In Fig. 2 the rearward position of part 44 is shown by the solid lineswhile the forward position of part 44 is indicated by the dot and dashlines in which the spaces between the legs of the U and the wedge part44 constitute reentrant areas for effectively producing the desiredturbulence.

Part 44 is actuated by a plurality of mechanisms spaced [around theafterburner 6. Each mechanism consists of three main parts: an actuatingdevice 52, an attaching means 54, and a connecting linkage 56.

The actuating device 52 consists of a cylinder 58, a piston 60 and apiston rod 62. The rearward end of the cylinder 58 is pivotally mounted.A lug 64 extends rearwardly from the rear end of cylinder' 58 and has ahole 66 therethrough. A bracket 68 is fixedly mounted on the afterburner6 and has an internally threaded bore 78. A bolt 72 passes through hole66 and is threadably engaged in bore 70. Bolt 72 may be fixed againstrotation by any means desired such as a cotter pin at 72'.

The free end of piston rod 62 has fixed thereon a bifurcated portion 74with a hole passing through both of the tines for a purpose to bedescribed later. The cylinder 58 has an opening 76 at its forward endand an opening 78 at its rearward end. Opening 76 is connected toconduit 36 by a conduit 80 having a valve 82 located therein and opening78 is connected to conduit 34 by a conduit 84 having a valve 86locatedtherein. It can be seen that if a pressure is admitted throughconduits'34 and 84 and valve 86 to the right side of pistons 60 and theleft sideofpistons 60, are vented, the pistons and their respectivepiston rods 62"will be moved to the left, and-if an operating pressureis admitted through conduits 36' and 80 and valve. 82 to'the left sideof pistons 60 andthe right side of pistons 60 are vented, the pistonsand'their respective piston rods 62 will be moved to the right. Whilethe selection and admission of the actuating pressure and connection todrain can be performed manually, an automatic control can perform suchfunction as referred to above.

Attaching means 54 consists of a flat plate 88 fixed to the flatforward-portion of part 44011; to'which is fixed two members 90 formingabifurcated bracket. These members have integralreinforcing ribs 92=toadd support to the structure. A hole 94.is located attire forward endofeach of'the members 90 for-a purpose to be disclosed hereinafter.

The connecting linkage 56 connects the actuatingdevice 52 to theattaching means 54. This connecting linkage 56 consistsof a rod 87mounted for rotation at one end in part 42 of the flameholder 22 and atthe other'end in the wall of afterburner 6. The mounting in part 42consists of two bearing members 96 and 98 which are fixed therein andcoaxially positioned. The interior diameter of bearing 96 is sized so asto receive the diameter of rod 87 and the interior diameter of bearing93 is sized so as to receive the necked down end portion 100 of rod 87.The mounting in the wall of the afterburner consists of one bearingmember 102 whichis fixed to a pad 104 men annular reinforcing plate 106which extends around the afterburner. These bearings 102 also extendinto the interior of the afterburner to form a support for the outersections 50 of the strut structure 46. This is accomplished by having aplate 108 fixed to the outer end of the sections 50 with a bearingreceiving member 110 therein. In the construction a space 112 is left toallow for radial expansion,

Rod $7 is attached at its end within part 42 to the bracket on theforward portion of part 44 by a lever 114. One end of lever 114 is fixedto rod 87 between the free ends of bearings 96 and 98 by any meansdesired such as by a pin 113. The other end of lever 114 is positionedbetween the free ends of the bracket formed on the forward portion ofpart 44 and is connected thereto by a pin 116 which passes through theend of said lever arm and the holes 94 located at the forward end ofeach of the members 90. This pin 116 permits relative movement at thispoint and is maintained in place by any means desired such as by cotterpins. A spacer 118 is located on each side of arm 14 around said pin 116and is weldedto member 90 to provide bearing area.

The end of rod 87 outside of said afterburner is connected to thebifurcated portion 74 of the actuating device 52 by a lever arm 120.This lever arm 120 is fixed to the outer free end of rod 87 by any meansdesired such as by a pin 122. The other end of lever 120 is positionedbetween the tines of the bifurcated portion 74 and has a hole thereinwhich is aligned with the holes in said tines. A bolt 124 passes throughsaid holes permitting relative movement at this point.

Operation When the engine is operating without afterburning, theposition of the flameholder 22 and nozzle.24 along with their respectiveoperating mechanisms will be in their positions as shown in Fig. 1. Whenthe engine is functioning in this manner, with valves 38, 40, 82 and 86open, an actuating pressure is directed through conduit 36to the leftside of cylinder 26 and through conduit 30 to the left side of. cylinder58. At the same time the right sides of. cylinders 26 and 58 are vented.This places the flameholder 22 in its streamlined position, that 4 iswith part 44 thereof in its rearward position, so that itspresence inthe airstream produces a minimum ofturbulence and pressure loss.; Thisaction also places the nozzle 24 in its closed position.

Now, when engine operation is desired with aftcrburning, an actuatingpressureis directed through conduit 34 to the right side of cylinder 26and through conduit 84 to theright side of cylinder 58. At the same timethe left sides of cylinders 26 and 58 are vented. This placesflameholder 22 in its flame holding position, that is with part 44thereof in its forward position, so that part 42. effects a reduction ofvelocity thereby stabilizing combustion within the afterburner. Thisaction also places the nozzle 24 in its open position.

While a manual system can be used to transfer the actuating pressure andventing to either conduit 34 or 36 it is to be understood that anautomatic means may be provided to perform this operation.

In the operation described above it has been considered thattheflameholder 22 and nozzle 24 are actuated simultaneously. However, ifit is desired to have either the flameholder or nozzle operate firstthis can be controlled by the use of the valves 38, 40, 82 and 86. Forexample, if it is desirous to have the flameholder operated before thenozzle, the valves 38 and 40 may be closed leaving valves 82 and 86 openso that when the conduits 34 and 36 have their connections interchanged,that is from actuating pressure to drain which ever may be the case, thefiameholder will be actuated alone and after a predetermined timeinterval the valves 38 and 40 can be opened permitting the newinterchanged pressures to be admitted'to the cylinders 26 therebyactuating the nozzle.

Here again while this has been shown as a manual operation, automaticmeans may be used to provide such a delay in either the actuation of thefiameholder-or nozzle. For example, the valves can be used as variablerestrictions delaying the, action to one cylinder or the other. If afixed relation of delayed action is desired,

a fixed restriction may be placed in the proper conduitbe evident tothose skilled in the art that the invention is capable of variousmodifications and adaptations within the scope of the appended claims.

I claim:

1. In combination, a combustion chamber through which gases pass at highvelocities, an annular flameholder mounted in said chamber, saidfiameholder comprising'a member having two annular parts, a forward partand a rearward part, said forward part having a leading edge, surfacesextending aft and diverging from the leading edge, said surfacessubsequently converging and terminating in spaced relation to eachother, said rearward part having its forward end located within therearward end of said forward part, surfaces extending aft from saidforward end of said rearward part and converging and terminatingadjacent each other to form a trailing edge, means for placing therearward part of said flameholder substantially completely within saidforward part such that the converging surfaces on the rearward part arelaterally spaced from the adjacent terminating surfaces of the forwardpart.

2. In combination, a combustion chamber through which gases pass at highvelocities, an annular flameholder mounted in said chamber, saidflameholder comprising a member having two annular parts, a forward partand a rearward part, said forward part having a lead-' ing edge andsurfacesextending aft and diverging from the leading edge, said surfacessubsequently terminating in spaced relation to each other, said rearwardpart having its forward end located within the rearward end of saidforward part, surfaces extending aft from said forward end of saidrearward part and converging and terminating adjacent each other to forma trailing edge, and means for placing the rearward part of saidflameholder substantially compeltely within said forward part such thatthe entire area of the forward part at the trailing edge functions as a.flameholder.

3. In combination, a combustion chamber through which gases pass at highvelocities, an annular liameholder mounted in said chamber, saidflameholder comprising a member having two annular parts, a forward partand a rearward part, said forward part having a circular leading edgeand surfaces extending aft and diverging from the leading edge, saidsurfaces subsequently terminating in spaced relation to each other, saidrearward part having its forward end located within the rearward end ofsaid forward part, surfaces extending aft from said forward end of saidrearward part and converging and terminating adjacent each other to forma circular trailing edge, and means Within said forward part andconnected to said rearward part for moving the rearward part of saidflameholder forwardly as a unit into a position substantially withinsaid forward part.

4. In combination, a combustion chamber through which gases pass at highvelocities, an annular flameholder mounted in said chamber, saidflameholder comprising a member having two annular parts, a forward partand a rearward part, said forward part having a circular leading edgeand surfaces extending aft and diverging from the leading edge, saidsurfaces subsequently converging and terminating in spaced relation toeach other, said rearward part having its forward end located within therearward end of said forward part and having a radial dimensionsubstantially equal to the space between the spaced apart ends of saidsurfaces, said rearward part also including surfaces extending aft fromsaid forward end of said rearward part and converging and terminatingadjacent each other to form a circular trailing edge, and means withinsaid forward part and connected to said rearward part for moving therearward part of said flameholder forwardly as a unit into a positionsubstantially within said forward part with the converging surfaces ofthe rearward part spaced radially from the ends of the surfaces on theforward part.

5. In combination, a combustion chamber through which gases pass at highvelocities, a flameholder mounted in said chamber, said flameholdercomprising a member having two parts, a forward part and a rearwardpart, said forward part having a leading edge, surfaces extending aftand diverging from the leading edge, said surfaces subsequentlyterminating, said rearward part having its forward end located withinthe rearward end of said forward part, surfaces extending aft from saidforward end of said rearward part and converging and terminatingadjacent each other to form a trailing edge, means for placing the aftpart of said flameholder substantially within said forward part, saidlast named means including a bracket fixed to the forward end of therearward part of said flame holder and located within said forward part,a lever pivotally mounted at one end to and within the forward part ofsaid flameholder, the free end of said lever being connected to saidbracket, and means external to the combustion chamber for moving saidlever thereby moving the rearward part of said flameholder axially inrelation to the forward part.

6. In combination, a combustion chamber through which gases pass at highvelocities, an annular fiameholder mounted in said chamber, saidflameholder comprising a body having two annular parts, one part beingsubstantially U-shaped in cross section with the open end thereof facingdownstream and the other part being a movable wedge-shaped piece adaptedto be positioned within the U-shaped part and movable to a position toform with said part a streamlined body.

7. In combination. a combustion chamber through which gases pass at highvelocities, an annular flameholder mounted in said chamber, saidflameholder comprising a body having two annular parts, one part beingsubstantially U-shaped in cross section with the open end thereof facingdownstream and the other part being a movable wedge-shaped piece adaptedto be positioned within the U-shaped part to form reentrant areasbetween the legs of the U and the wedge shaped piece and movable to aposition to form with said part a streamlined body, and means accessibleexternally of said combustion chamber for actuating said movable wedge.

8. In combination, a combustion chamber through which gases pass at highvelocities, an annular flameholder mounted in said chamber, saidflameholder comprising a body having two annular parts, one part beingsubstantially U-shaped in cross section with the open end thereof facingdownstream and the other part being a movable wedge-shaped piece adaptedto be positioned within the U-shaped part and movable axially to aposition to form with said part a streamlined body, means accessibleexternally of said combustion chamber for actuating said movable wedge,said last named means including a bracket fixed to the forward end ofsaid wedgeshaped piece, a lever pivotally mounted at one end in theU-shaped part, the free end of said lever being connected to saidbracket, and means for moving said lever thereby moving the wedge-shapedpiece axially in relation to said U-shaped part.

9. In combination, a combustion chamber through which gases pass at highvelocities, an annular flameholder mounted in said chamber, saidflameholder comprising a body having two annular parts, one part beingsubstantially U-shaped in cross section with the open end thereof facingdownstream and the other part being a movable wedge-shaped piece adaptedto be positioned within the U-shaped part and movable axially to aposition to form with said part a streamlined body, means accessibleexternally of said combustion chamber for actuating said movable wedge,said last named means including a bracket fixed to the forward end ofsaid wedge-shaped piece, a lever pivotally mounted at one end in theU-shaped part, the free end of said lever being connected to saidbracket, a shaft fixed at one end to the pivot of said lever and havingits other end extend to the exterior of said combustion chamber, asecond lever fixed at one end to the end of said shaft extendingexternally of said combustion chamber, and means for actuating the freeend of said second lever.

10. In combination, a combustion chamber through which gases pass athigh velocities, -a nozzle controlling the opening at the rearward endof said combustion chamber, a cone having its apex projecting into theforward end of said combustion chamber forming an annular passageway forthe flow of gas into said combustion chamber, a flameholder mounted insaid combustion chamber and axially spaced downstream from said cone,said flameholder comprising an annular streamlined body having twoparts, the forward part of said streamlined body forming the forwardpart of said flameholder and being of flame holding shape, the rearwardpart of said streamlined body forming the rearward part of saidflameholder and being of substantially wedge shape, the forward part ofsaid flameholder having an opening therein to receive the rearward partof said flameholder for axial movement therein, said rearward part ofsaid streamlined body being mounted for axial movement with respect tosaid forward part such that said rearward part may be positioned withinsaid forward part of said streamlined body to provide a flameholdingshape.

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